在Cmake项目中使用特征库?

I am having difficulty using a header-only library (Eigen) in my CMake project. When i take off all the portion related to Eigen library it compiles, but not sure how to build with (Eigen). Note that Eigen has a CmakeLists.txt in Eigen folder, and it has /src folder having (*.h and *.cpp) related to Matrix operation etc...I am having difficulty using a header-only libr